Multi-cable medical instrument

Abstract

A medical instrument includes cable pairs respectively wound around input spindles and connected to actuate degrees of freedom of an instrument shaft structure. The cables may connect so that rotating the input spindles actuates corresponding degrees of freedom. First pulleys in the instrument may receive first cables from the input spindles and redirect the first cables toward the instrument shaft, and second pulleys may receive second cables from the input spindles and redirect the second cables toward the instrument shaft. In one configuration, the first and second pulleys are respectively mounted at first and second levels, and the second pulleys redirect the second cables through the first level. Additionally or alternatively, one level of cables may cross while the other level of cables does not.

What is claimed is: 
     
       1. A medical instrument comprising:
 a plurality of first cables, a first cable of the plurality of first cables being wrapped a first input spindle of the plurality of input spindles; 
 a plurality of second cables, a second cable of the plurality of second cables being wrapped around a second input spindle of the plurality of input spindles; 
 a chassis in which the plurality of input spindles is mounted; 
 an instrument shaft comprising a first end and a second end, the instrument shaft extending from the chassis at the first end; 
 a mechanical structure coupled to the second end of the instrument shaft, the mechanical structure having a plurality of degrees of freedom of motion, the plurality of first cables and the plurality of second cables being connected to the mechanical structure such that rotations of the plurality of input spindles actuate the plurality of degrees of freedom of motion; 
 a plurality of first pulleys mounted at a first level on the chassis, the plurality of first pulleys receiving the plurality of first cables from the plurality of input spindles and redirecting the plurality of first cables toward the instrument shaft; 
 a plurality of second pulleys mounted at a second level on the chassis different from the first level, the plurality of second pulleys receiving the plurality of second cables from the plurality of input spindles and redirecting the plurality of second cables through the first level and toward the instrument shaft; 
 a first piece on which the plurality of first pulleys is mounted; and 
 a second piece mounted over the first piece so that the plurality of first pulleys is located between the first piece and the second piece, the second piece being between the plurality of first pulleys and the plurality of second pulleys, the first piece and the second piece shaped to provide a close fit between the first piece and the plurality of first pulleys and configured to prevent the plurality of first cables from being derailed when the first piece and the second piece are coupled together. 
 
     
     
       2. The medical instrument of  claim 1 , wherein:
 the plurality of first cables extends between the plurality of input spindles and the plurality of first pulleys without crossing; and 
 a first set of the plurality of second cables crosses a second set of the plurality of second cables between the plurality of input spindles and the plurality of second pulleys. 
 
     
     
       3. The medical instrument of  claim 2 , wherein:
 the first cable is wrapped around the first input spindle and the second cable is wrapped around the second input spindle, the first cable is directed toward a location on a first side of a central axis of the instrument shaft and the second cable is directed toward a location opposite the first side of the central axis of the instrument shaft. 
 
     
     
       4. The medical instrument of  claim 2 , wherein:
 the plurality of input spindles is arranged in an array; 
 the first cable of the plurality of first cables is wrapped about the first input spindle in a direction such that a path of the first cable from the first input spindle to the plurality of first pulleys emerges within the array; and 
 the second cable of the plurality of second cables is wrapped about the second input spindle in a direction such that a path of the second cable from the second input spindle to the plurality of second pulleys emerges from a perimeter of the array. 
 
     
     
       5. The medical instrument of  claim 1 , wherein:
 the first cable wraps around the first input spindle in a first direction, and the second cable wraps around the second input spindle in a second direction opposite the first direction. 
 
     
     
       6. A method for assembling a medical instrument comprising:
 mounting a plurality of first pulleys on a first piece of a chassis of the medical instrument; 
 feeding a plurality of first cables from an instrument shaft of the medical instrument over the plurality of first pulleys; 
 attaching a second piece of the chassis to the first piece so that at least a portion of the plurality of first cables is between the plurality of first pulleys and the second piece; 
 mounting a plurality of second pulleys on the chassis in positions such that the second piece is between the plurality of second pulleys and the plurality of first pulleys; and 
 feeding a plurality of second cables from the instrument shaft over the plurality of second pulleys, 
 the first piece and the second piece shaped to provide a close fit between the first piece and the plurality of first pulleys to prevent the plurality of first cables from being derailed when the first piece and the second piece are attached together. 
 
     
     
       7. The method of  claim 6 , wherein:
 gaps between the second piece and the plurality of first pulleys are narrower than a width of the plurality of first cables. 
 
     
     
       8. The method of  claim 6 , further comprising:
 attaching a third piece of the chassis to the first and second pieces so that at least a portion of the plurality of second cables is between the plurality of second pulleys and the third piece. 
 
     
     
       9. The method of  claim 6 , further comprising:
 winding a first cable of the plurality of first cables around a lower portion of an input spindle; and 
 winding a second cable of the plurality of second cables around an upper portion of the input spindle, wherein the second cable and the first cable wrap around the input spindle in opposite directions. 
 
     
     
       10. The method of  claim 9 , wherein winding the first cable around the input spindle comprises:
 winding the first cable on a first capstan until the first cable has a desired tension, and affixing the first capstan on the input spindle. 
 
     
     
       11. The medical instrument of  claim 1 , wherein:
 the first cable is wrapped around the first input spindle and the second cable is wrapped around the second input spindle, the first cable is directed toward a location on a first side of a central axis of the instrument shaft and the second cable is directed toward a location opposite the first side of the central axis of the instrument shaft. 
 
     
     
       12. The medical instrument of  claim 1 , wherein:
 the plurality of input spindles is arranged in an array; 
 the plurality of first cables is wrapped about the plurality of input spindles in directions such that paths of the plurality of first cables leading from the plurality of input spindles to the plurality of first pulleys emerge within the array; and 
 the plurality of second cables is wrapped about the plurality of input spindles in directions such that paths of the plurality of second cables leading from the plurality of input spindles to the plurality of second pulleys emerge from a perimeter of the array. 
 
     
     
       13. A medical instrument comprising:
 a chassis comprising a mounting piece, a first pulley, and a second pulley; 
 the first pulley configured to rotate about an axle; and 
 the mounting piece coupled within the chassis between the first pulley and the second pulley, the mounting piece comprising a first portion and a second portion, the first portion of the mounting piece at least partially covering the first pulley, the second portion defining a groove within which the axle is mounted; 
 a shaft comprising a first end and a second end, the first end of the shaft being coupled to the chassis; 
 a jointed mechanism coupled to the second end of the shaft, the jointed mechanism having a mechanical degree of freedom; 
 means for pulling a first cable, the first cable extending from the means for pulling the first cable, across the first pulley, through the shaft, and to the jointed mechanism; and 
 means for pulling a second cable, the second cable extending from the means for pulling the second cable, across the second pulley, through the shaft, and to the jointed mechanism; 
 wherein the first and second cables actuate the mechanical degree of freedom of the jointed mechanism. 
 
     
     
       14. The medical instrument of  claim 13 , wherein:
 the chassis comprises a third pulley and a fourth pulley; 
 the jointed mechanism has a second mechanical degree of freedom; and 
 the medical instrument further comprises:
 means for pulling a third cable, the third cable extending from the means for pulling the third cable, across the third pulley, through the shaft, and to the jointed mechanism; 
 means for pulling a fourth cable, the fourth cable extending from the means for pulling the fourth cable, across the fourth pulley, through the shaft, and to the jointed mechanism; 
 wherein the third and fourth cables actuate the second mechanical degree of freedom of the jointed mechanism. 
 
 
     
     
       15. The medical instrument of  claim 14 , wherein:
 the second cable crosses the first cable between the means for pulling the second cable and the second pulley. 
 
     
     
       16. The medical instrument of  claim 14 , wherein:
 the second cable crosses the first cable and the fourth cable between the means for pulling the second cable and the second pulley. 
 
     
     
       17. The medical instrument of  claim 14 , wherein:
 the second cable crosses the first cable and the fourth cable between the means for pulling the second cable and the second pulley; and 
 the fourth cable crosses the second cable and the third cable between the means for pulling the fourth cable and the fourth pulley. 
 
     
     
       18. The medical instrument of  claim 13 , wherein:
 the means for pulling the first cable and the means for pulling the second cable is a spindle around which the first cable is wrapped in a first direction and the second cable is wrapped in a second direction opposite the first direction. 
 
     
     
       19. The medical instrument of  claim 13 , wherein:
 the means for pulling the first cable comprises a first spindle around which the first cable is wrapped; and 
 the means for pulling the second cable comprises a second spindle around which the second cable is wrapped. 
 
     
     
       20. The medical instrument of  claim 1 , wherein:
 the plurality of first pulleys redirects the plurality of first cables into and through the instrument shaft; and 
 the plurality of second pulleys redirects the plurality of second cables through the first level and into and through the instrument shaft. 
 
     
     
       21. The medical instrument of  claim 13 , wherein:
 the first cable extends from the means for pulling the first cable, across the first pulley, into and through the shaft, and to the jointed mechanism; and 
 the means for pulling the second cable includes means for pulling the second pulley into and through the shaft, and to the jointed mechanism.